H.323 is an International Telecommunications Union (ITU) standard that provides a foundation for audio, video, and data communications across packet-based networks, including the Internet. Compliance with the H.323 standard permits interoperability, allowing users to communicate without concern about non-compatibility. The H.323 recommendation provides a standard for multimedia communications over packet switched networks . Such networks include many corporate networks, packet-switched TCP/IP networks, IPX over Ethernet, Fast Ethernet and Token Ring technologies, public Internet, ATM networks, and/or others. H.323 enables videoconferencing as well as addressing call control, multimedia management, and bandwidth management. Thus, H.323 encompasses inter-network multipoint conferencing among terminals that support not only audio, but also video and data communication.
Use of multimedia communications over packet-based networks has increased as an alternative form of communication due in part to the expense of the use of public-switched telephone networks (PSTN)/integrated services digital networks (ISDN). However, the packet-switched traffic can also be sent over the circuit-switched PSTN network (e.g., IP-over-PPP-over-PSTN or IP-over-PPP-ISDN), and H.323 packet bitstreams can be sent over them. Rapid expansion of packet-based networks has made the need for interoperable equipment and systems more urgent. While the H.323 has addressed terminal mobility, it has not provided a user, service and service provider mobility framework, which is needed for both the wired and wireless environment.